Retrievable subsurface well safety valves are utilized in oil and/or gas wells for installation in the well production conduits for protecting the well. Such valves are installed and retrieved by various methods such as wireline operations or pumpdown operations. However, retrievable safety valves which are inserted into the well conduit restrict the well bore and thereby restrict and reduce the amount of well production that can be obtained through the well conduit. One common type of safety valve is the flapper type valve shown in U.S. Pat. No. 4,161,219. The flapper valve is positioned in a valve housing and a flow tube or tubular member telescopically moves through the housing for controlling the movement of the flapper in response to a hydraulic piston and cylinder assembly.
However, flapper valves restrict and limit the size of the bore through the valve. As disclosed in U.S. Pat. No. 4,531,587, a curved or arcuate flapper valve has been used so that in the open position a larger bore may be provided in the valve thus enlarging the valve flow area.
Also, retrievable safety valves require an annular hydraulic chamber for mating with a hydraulic fluid control port in the well conduit for actuating the valve piston and cylinder assembly. This hydraulic chamber again takes up space and reduces the area of the bore through the valve.
One feature of the present invention is the provision of a curved or arcuate flapper type retrievable safety valve in which the valve seat and arcuate flapper are connected to the bottom of the valve housing thereby further increasing the available space for enlarging the bore through the valve housing. In this case, the well conduit acts as a protective housing. A nose separate from the valve housing is provided to coact with the flow tube or tubular member to protect the valve seat and the valve closure member when the valve is in the open position.
Another feature of the present invention is the provision of a retrievable safety valve having a control fluid passageway which extends from the piston and cylinder assembly to a single circumferential position on the exterior of the housing and in which the housing may be oriented to bring the fluid passageway into alignment with a hydraulic control port in the well conduit. This feature again allows an increase in the cross-sectional area of the bore through the housing.
As an example, a 41/2" retrievable well safety valve constructed in accordance with U.S. Pat. No. 4,161,219 has an internal diameter of 2.125 inches which provides a cross-sectional area of 3.5 square inches. By utilizing the structure of the present invention, a 41/2" retrievable safety valve may be provided having an internal diameter of 2.765 inches which provides a cross-sectional area of 6.0 square inches thereby increasing the well production through the valve.